1. Field of the Invention
The present invention relates to a developing apparatus for an electrophotographic device, and more particularly to a center-feed type developing apparatus.
2. Description of the Related Art
Referring to FIG. 1, a conventional center-feed type developing apparatus will be described.
The conventional center-feed type developing apparatus includes two developing rolls 5 and 8 which are set opposite to a photosensitive drum 7 in a developing container 1 in such a manner that the two developing rolls are rotatable in different directions. The developing apparatus also includes a developing agent 3 in the developing container 1 which is drawn up by a conveyor roll (unnumbered) toward the developing rolls 5 and 8 and regulated by a first developing agent regulating member 11 before being distributed by a second developing agent regulating member 12 to the developing rolls 5 and 8.
With the arrangement described above, the second developing agent regulating member 12 is provided on the side of the photosensitive drum 7 with respect to a line connecting the centers of the developing rolls 5, 8 as a boundary. Consequently, the toner which has scattered tends to accumulate on the surface of the second developing agent regulating member opposite to the photosensitive drum 7 (a portion D). The toner that has accumulated on the portion D falls in drops on the developing roll 5 by its own weight and leaves a toner stain on recording paper. The toner that has fallen on the developing roll 5 may spoil images or stick to the photosensitive drum 7, thus causing a fog.
In order to deal with this problem, Japanese Patent Examined Publication No. Hei 2-8308 discloses a method of preventing the accumulation of a toner by contriving to arrange the magnetic flux of developing magnetic poles so as to let a developing agent 3 fall on the part D of a second developing agent regulating member 12. On the other hand, Japanese Utility Model Examined Publication No. Sho 59-26372 discloses, as shown in FIG. 2, a method of preventing the accumulation of a toner by fitting a film 13 to a second developing agent regulating member 12, the film 13 being caused to vibrate by contact with a developing agent layer.
As set forth above, the prior art center-feed type developing apparatus is equipped with the developing agent regulating member which is located on the photosensitive drum side with respect to the line connecting the centers of two developing rolls as a boundary. As a result, the scattered toner easily accumulates on the opposite surface of the developing agent regulating member to the photosensitive drum, thus causing a fog as well as the deterioration of image quality.
Since the developing agent regulating member is installed in a small space between the two developing rolls, rigidity essential to regulating the developing agent is unavailable in the case of a developing apparatus designed to deal with broad recording paper, which results in an unstable regulated quantity of the developing agent.